Incandescent electric lamp



June 11, H V N HORN ET AL 1,717,283

INCANDESCENT ELECTRIC LAMP Filed Dec. 8, 1925 1 INYENTURS: 24 IRVINE H S/Azszfi'anm Wizzua A. PJPKIN,

Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

IRVING H. VAN HORN AND WILBUR A. PIPKIN, OF EAST CLEVELAND, OHIO, AS SIGNOBS TO GENERAL ELECTRIC COMPANY, A CORPORATION 01 NEW YORK.

INCANDESCENT ELECTRIC LAMP.

Application filed December 8, 1925. Serial No. 74,115.

Our invention relates to series electric incandescent lamps and more particularly to means for preventing the extinguishment of the lamps upon a failure of the filament of 6 one of them. At present the situation is taken care of by providing in each lamp an automatic cut-out device similar to that shown in our pending application, Serial No. 698,502, automatic cut-outs for electric incandescent lamps, filed March 11, 1924. That device has the disadvantage that the failed lamp oes out, being short-circuited, and the other amps continue to burnat a slight increase in voltage. The object of the present invention is to overcome this disadvantage.

According to our invention we provide the series incandescent lamp with a plurality of filaments and means for automatically cutting in the other filament when one filament fails. This improvement is particularly advantageous in the case of lamps operated in series on street railway or street lighting service where current is supplied from con stant voltage supply mains. For example,

if twenty lamps were operated on 600 volt D. G. street railway service, the failure and consequent shorting out of one, two, three, or four lamps would result in a corresponding increase of five and three-tenths per cent,

eleven and one-tenth per cent, seventeen and seven-tenths per cent, and twenty-five per cent in volts on the remaining nineteen, eighteen, seventeen, and sixteen lamps respectively. By providing an extra or seeondary filament in each lamp, we insure that this increase in voltage does not occur and that the failure of one or more lamps in the series will not interfere with the performance of the remaining lamps. We contemplate making the secondary filament of somewhat lower candle power so that the lamp affected may be readily detected and replaced.

In the drawing, Fig. 1 is a front elevation of 1 our im roved lamp; Fig. 2 is a side elevation thereo Fig. 3 is a horizontal section along the line 33 of Fig. 1; Fig. 4 is a partial horizontal section on an enlarged scale of one of the bridge members; Fig. 5 is an elevation thereof; Fig. 6 is an elevation of a portion of the lamp showing the operation of our invention under one condition, and Fig. 7 is a perspective of the film cut-out.

As shown in the drawing, the incandescent lamp comprises a bulb 10 having the usual base 11 and stem 12 in which are sealed 9. pair of leading-in conductors and filament supports 13 and 14. A filament 15 of the coiled type, and preferably. of tungsten, is clamped at the ends ofthe supports 13 and 14, and is held in position by means of a support wire 16 which is fused into a glass rod 17 extending from the stem 12. An auxiliary filament 18, preferably of lower candle power than the filament 15, is clamped to the ends of the support wires 19 and 20 which extend from the button 21 formed on the rod 17. The wires 19 and 20 are connected to the conductors 13 and 14 by means of the bridge members 22 and 23, which are preferably in the form of thin strips of metal )ent around the wires, as shown in Fig. 4. Between one of these members, 22 as shown, and the corres onding conductor 13, there is interposed :1. lm cut-out 24 which may be composed of sheet aluminum coated with a thin film of aluminum oxide 25. This is preferably bent around the conductor 13 so that it rigidly maintains its position.

In operation a number of lamps are electrically connected in series and when the current is on, the path of the circuit is normally through the conductor 12, primary filament 15, and conductor 13. In the case of a gasfilled lamp when the filament 15 is broken during service, an arc will occur between one end of the filament and one end of the conductor 13 which melts back, as shown in Fig. 6, in the form of a ball 26 until the heat caused by the arc rises high enough to break down the insulating film 25 thereby forming an electrical connection between the conductor 13 and wire 19, substituting secondary filament 18. In some cases the insulating film 25 may not break down but will be short circuited when the ball of molten metal 26 reaches the bridge member 22.

In the case of a vacuum lamp, the failure of filament 15 would always result in the electrical breakdown of the insulating film 25, without the melting back of the conductors, because the voltage required to sustain an arc in a vacuum is always high enough to puncture the insulating film. Should the filament 15 be broken when the lamp is out of service, the insulating film 25 is electrically broken down when the full circuit voltage is applied. This applies to both vacuum and gas-filled lamps.

What we claim as new and desire to secure I by Letters Patent of the United States, is,

1. In an electric incandescent lamp, the combination of a filament, a conductive support electrically connected with said filament and with a terminal of said lamp, another filament, an independent conductive support therefor, and a normally insulating memher in contact with each of said supports and adapted to become conductive upon failure of the first-mentioned filament.

2. In anelectric incandescent lamp, the combination of a filament, a conductive support electrically connected with said filament and with a terminal of said lamp, another filament, an independent conductive support therefor, and a film cut-out in contact with each of said supports and adapted to become conductive upon failure of the first-mentioned filament. e

3. In an electric incandescent l-amp, the combination of a filament, a conductive support electrically connected with said filament and with a terminal of said lamp, another filament, an independent conductive support therefor, and a coated metalstrip in contact withcach of said supports and adapted to become conductive upon failure of the firstmentioned filament.

4. In an electric incandescent lamp, the combination of a filament, a pair of conductive supports electrically connected with said filament and the lamp terminals, another filament, independent conductive supports therefor, and normally insulating members each separating one of the firstmentioned supports from one of those second mentioned and adapted to become conductive upon the failure of the first-mentioned filament.

5. In an electric incandescent lamp, the combination of a filament, a pair of conductive supports electrically connected with said filament and the lamp terminals, another filament, independent conductive supports therefor, and-film cut-outs each separating one of the first-mentioned supports from one of those second mentioned and adapted to become conductive upon the failure of the first-mentioned filament.

6. In an electric incandescent lamp, the combination of a filament, a pair of conductive supports electrically connected with said filament and the lamp terminals, another filament, independent conductive supports therefor, and coated metal strips each separating one of the first-mentioned supports from one of those second mentioned and adapted to become conductive upon the failure of the first mentioned filament.

7. In an electric incandescent lamp, the combination of a filament, a conductive support electrically connected with said filament and with a terminal of said lamp, another filament, an independent conductive support therefor, and a normally insulating member in contact with each of said supports and supported thereby, and adapted to become conductive upon failure of the first mentioned filament.

8. In an electric incandescent lamp, the

combination of a filament, a conductive support electrically connected with said filament and with a 't'erminal of said lamp, another filament of lower candle power than the first-mentioned filament, an independent conductive support therefor, and a normally insulating member in contact with each of said supports and adapted to become conductive upon failure of the first-mentioned filament.

9. In an electric incandescent lamp, the combination of a filament, a conductive support electrically connected with said filament and with a terminal of said lamp, another filament, an indenendent conductive support therefor, and a coated metal strip in contact with each of said supports and wrapped therearound, and adapted to become conductive upon failure of the firstcember, 1925.

IRVING H. VAN HORN. WILBUR A. PIPKIN. 

